Donnatal: Full prescribing information from RxList.Donnatal Extentabs - PBM Pharmaceuticals: Official Pharmaceutical Website with information for consumers and health professionals.MedlinePlus: Belladonna Alkaloid Combinations and Phenobarbital: Provides information about dosage, usage, warnings, and side effects.MedlinePlus: Belladonna Alkaloids and Barbiturates (Systemic): Provides information about dosage, usage, warnings, and side effects.